Technical Abstract:
Two component sensor-response regulator systems have been implicated in genetic modulation by environmental cues in a wide variety of prokaryotic backgrounds. Mutations in the sensor gene lemA have pathovar-specific effects in plant-pathogenic Pseudomonas syringae. Hybridization experiments indicate that this gene is widely distributed within Pseudomonas. We have isolated the lemA homolog from P. aeruginosa and this homolog fully restored the phenotypes of P. syringae lemA mutants. We have constructed site-specific mutations in the lemA gene and the cognate response regulator gene, gacA , of P. aeruginosa. Mutants containing defects in either of these genes were found to be defective in the production of pyocyanin and showed an altered colony morphology. The sequence of the P. aeruginosa strain PAO lemA gene has been determined and submitted to GenBank (accession number AF030352). This sequence reveals that the predicted PAO lemA ORF is 68% identical in amino acid sequence to the P. syringae pv. syringae LemA protein. This data reveals that the lemA protein is indeed highly conserved within the genus Pseudomonas.